This training grant sets forth a combined research training program for five MD or PhD post-doctoral fellows per year in Rheumatology/Immunology, Pediatric Rheumatology, and Orthopedics at New England Medical Center, Tufts University School of Medicine. Our goal is to provide supervised research in the laboratory under the guidance of an accomplished faculty mentor, along with structured training in molecular biology and immunology, biostatistics, and ethical issues through courses or conferences. Specific actions are being taken to increase the number of applicants from underrepresented ethnic and racial minority groups. The research thrust of the Rheumatology/Immunology Division is the study of infectious agents, immunity, and cytokines in chronic inflammatory arthritis, particularly Lyme arthritis. Because of new faculty with research interests in the Orthopedics Department here and because of the planned merger of New England Medical Center with the New England Deaconess and New England Baptist Hospitals, the scope of our training program is being broadened to include research training for rheumatologists, orthopedic surgeons, and basic scientists in disorders of cartilage and bone. Of the 11 faculty sponsors who participate in this training program, 5 are from adult rheumatology, 1 from pediatric rheumatology, 2 from orthopedics, 1 from infectious diseases, and 2 from the Molecular Biology and Microbiology or Pathology Basic Science Departments. These investigators and their trainees form a rich network for interactions and collaborative research projects relevant to rheumatic disease research. The success of the program is attested to by the fact that 5 of the 6 graduates of the program have secured faculty positions in academic medical centers. The participation of faculty members and trainees from adult and pediatric rheumatology, orthopedics, and basic science departments in this training program offers a unique opportunity for research training in arthritis and musculoskeletal diseases.